Target, which operates nearly 1,800 stores in the U.S., said the incident occurred when a computer virus infiltrated the terminals at registers where shoppers swipe their credit or debit cards to purchase items.

TJX Companies, which operates T.J. Maxx and Marshall's stores, was the victim of the largest security breach, in 2006. That one affected more 94 million domestic and international accounts with credit card, debit card ,and check information, including 65 million Visa customers. Ten months later, Visa reported between $68 million and $83 million in fraud-related losses to banks and other institutions.